From the SECS Bylaws:

The procedure for determining winners in secret ballots shall be the following. Given n positions to be filled, each voter shall vote for not more than n candidates. The winner(s) are those r candidates, r <= n, receiving the highest vote totals equal to or greater than 40 percent. If r < n, a runoff election is held among those q non-elected candidates who received the highest vote totals. The winners of this runoff are the n-r candidates receiving the highest vote totals. The formula for determining q is:

q = 2(n-r-1) + (n-r-1)(n-r-2)/2(n-r-3) + n-r-(n-r-1)2

valid for 1 <= (n-r) <= 5

Input the values in blue

Number of ballots cast
Minimum number of votes received to win (40% of ballots cast)
Positions to be filled, n
Number of candidates receiving more than the minimum number of votes, r
Number of candidates in run-off election, q